The present invention relates generally to a support disk for a rotor spinning device and more particularly to a support disk having openings located in the measuring range of a sensor device using a light source to emit a light beam to a receiving device.
In a customarily used design of a rotor spinning device, the spinning rotor is mounted by its rotor shaft in the nip of two pairs of support disks and is driven by a tangential belt which acts on the rotor shaft from above. One of the pair of support disks which are located most outwardly relative to the rotor, comprises means on the outer side facing a light source which serves to intermittently reflect the incident light or intermittently interrupt the reflection of the light. Part of the reflected light of the light source strikes a measuring device and is converted into signals for measurement of the rotor speed. If, for example, a yarn break occurs at the spinning location, it is detected via a monitoring of the yarn and the rotor of this spinning location is stopped. The stopping of the support disks associated with the rotor is then recognized by the absence of signals for the speed measurement. A signal requesting a spinning-start carriage follows in order to correct the yarn break and to start spinning the yarn again. The broken yarn ends are automatically rejoined by a splicing or piecing operation during the startup time of the rotor at a certain speed which is significantly lower than the spinning speed of the rotor. When the rotor has attained the particular speed favorable for the splicing/piecing operation, the spinning-start carriage performs the automatic joining of the yarn ends. After the reconnection of the yarn ends has taken place, the rotor does not attain its spinning speed until after a further startup time since the tangential belt must still accelerate the rotor and the support disks up to this spinning speed. The speed monitoring and speed control are of considerable significance for attaining and maintaining of the required yarn parameters.
Such rotor spinning devices are described, for example, in German Patent Publications DE 41 21 387 A1 and DE 195 31 660 A1. German Patent Publication DE 195 31 660 A1 teaches that, for an operationally reliable and rapid detection of the speed and of changes in the speed during an acceleration phase or braking phase of the rotor of rotor spinning machines, the receiving system of a reflection light barrier is adjusted to reflex light from an illuminating light beam and to scatter the reflex light on a main surface of the rotating body of a support disk having at least one bore on the line of the light beam, the bore being slightly reflective for the entire light beam relative to the main surface of the support disk body and acts like a light trap. In particular, the action of the bore as a light trap or light sink is important to essentially eliminate light scattering in order to achieve a sufficient contrast for error-free speed measurement even in the case of a main disk body surface which reflects light only weakly.
During the operation of the rotor spinning device, deposits of dirt and fibers settle in the bore of the support disk. The bore gradually grows from the outside toward the inside in the direction of the axis of rotation as a result of such deposits of dirt and yarns, which can prevent a distinct contrast to be registered by the receiving system between the light scattered by the main surface of the rotating support disk body and the non-reflected light entering the particular bore.
Furthermore, reflection light scanners are known from German Patent Publication DE 195 31 660 A1 in which light emitters and light receivers are supported in a housing as in a reflection light barrier. The presence of the light spot, e.g., of a laser light spot, is detected in an image plane with such light scanners. The surface of the support disk acts as an image plane. When the light spot dips into an opening its image is distinctly behind it and is no longer recognized. There is still the danger of a contamination on the support disks, primarily by fluff formation, which hinders the operational reliability of the speed measuring operation. Dirt settles especially in through openings of the support disks, as is schematically shown in FIG. 5 of this patent.
German Patent Publication DE 41 21 387 A1 teaches lateral disks set on the lateral surfaces of the support disks which lateral disks cover the bores in the support disk and therewith prevent such deposits of dust and yarns. These superimposed lateral disks represent additional required structural components which have to be mounted and render a distinct contrast between the scattered light reflected from the surface of the support disk and between the light entering the particular bore more difficult due to their reflection behavior, thereby preventing a reliable recognition of signals.
German Patent Publication DE 43 13 753 A1 teaches a support disk for a support-disk bearing of open-end spinning rotors in which a front side is provided with signal generators for a contactless speed measuring which operate by means of magnetic field lines. Permanent-magnet pins are fit into the support disk which generate an induction current. In another embodiment of the support disk of aluminum or plastic, the signal generator is constructed of ferromagnetic material.
In a further version of this known support disk the main casting of the support disk consists of steel and the signal generator is a bore let into the main casting. An electric signal can also be collected in this manner. The induction current produced is supplied via an electric line to an evaluation device which is connected to various control motors of the spinning-start device. This inductive method is intended to prevent imprecise signals from being supplied when the support-disk pairs are clogged with fluff. The pulse sensors must be positioned relatively close to the surface of the main casting of the support disks in order to assure sufficient precision and strength of the signals. The creation of disturbing air vortices given the necessary position of the pulse sensors near the surface is a disadvantage. Given the high speed of the support disk, even two bores in the front side of a support disk bring about air blasts of such a strength that the bores can also be used as signal generators in association with pulse sensors positioned near the surface for a speed measurement in which the particular air blast is registered and evaluated as a signal, as explained in German Patent Publication DE 43 13 753 A1 in column 2, lines 34 to 38.